In air purifiers and air conditioners and the like, a multiblade fan is used in order to perform blowing. As a conventional example, FIG. 1 and FIG. 2 show an example of a single suction type multiblade fan. Here, FIG. 1 shows a side view (specifically, an A-A cross-sectional view of FIG. 2) of the conventional single suction type multiblade fan, and FIG. 2 shows a plan view of the conventional single suction type multiblade fan.
A multiblade fan 10 is configured by an impeller 13, a casing 11 that houses the impeller 13, a motor 14 for driving the impeller 13 to rotate and the like. Here, axis O-O in FIG. 1 and FIG. 2 is the axial line of rotation of the impeller 13 and the motor 14.
In the impeller 13, one end of each of numerous blades 33 (in FIG. 2, just some of the numerous blades 33 are shown) is fixed to an outer peripheral portion of one side of a discoid main plate 31, and outer peripheral edges of the other ends of the blades 33 are connected to each other by an annular side plate 32.
The casing 11 includes a suction opening 11a that sucks in gas from one side in the rotational axis O direction and a blowout opening 11b that blows out gas in a direction intersecting the rotational axis O. The periphery of the suction opening 11a is surrounded by a bellmouth 12 that leads to the impeller 13. Additionally, the suction opening 11a is disposed so as to face the side plate 32. Further, the blowout opening 11b is disposed so as to blow gas in the direction intersecting the rotational axis O.
When the motor 14 is driven to cause the multiblade fan 10 to run, the impeller 13 rotates in the rotational direction R of FIG. 2 with respect to the casing 11. Thus, the blades 33 of the impeller 13 boost the pressure of and blow out gas from the space on the inner peripheral side to the space on the outer peripheral side, the gas is sucked from the suction opening 11a into the space on the inner peripheral side of the impeller 13, and the gas blown out to the outer peripheral side of the impeller 13 is gathered in the blowout opening 11b and blown out (e.g., see JP-A No. 9-209994).